A large number of such field devices, which are integratable in such a decentralized automation system, are manufactured and sold by the firm Endress+Hauser.
Progress in the field of microelectronics in recent years has led to a miniaturizing of devices and integration of functionalities. This has brought about effective and cost-favorable application of such integrated, decentralized systems in automation technology. Thus, in field devices with sensors and actuators, not only are measured values ascertained, but, also, the measured values are preprocessed and linearized, and self-diagnosis routines are implemented in the sensors or actuators. Prerequisites for introduction of these decentralized functionalities into a closed, automation design with “intelligent” sensors and actuators are increased information exchange between the decentralized units and, further, the preprocessing and storing of data and parameters in the units.
As a rule, decentralized units, or field devices, in modern automation installations are connected with a control system via a fieldbus, e.g. Profibus, Foundation Fieldbus. The control system serves for process control, process visualization, and process monitoring, as well as for configuring and parametering the decentralized units, or field devices.
The individual field devices perform various functions within the decentralized automation system. For special, standard functions, e.g. a PID-controller, so-called function blocks are available with defined communication interfaces. These function blocks form, with corresponding algorithms, which are executed in the microprocessors of the individual field devices, special application functions. In order that these function blocks can communicate with one another, an essential aspect of the function blocks resides in their having defined interfaces, so that they can be simply linked for complex control strategies of an automation system. In the Foundation Fieldbus specifications, various standard function blocks are specified. Typical function blocks for field devices are, for example, analog input AI, analog output AO, and PID-controller PID. Fieldbus Foundation has specified flexible function blocks, which are freely programmable according to the IEC-standard 61131.
Before a decentralized unit, or field device, can be used in a decentralized automation system, it must be configured and parametered. Necessary to accomplish this is, among other things, the loading of the control strategy into the corresponding field devices. Known applications enabling this loading include, for example, the SysCon system of the firm, SMAR, or DeltaV of the firm, Emerson. With these applications, it is also possible to test the correct networking of the individual function blocks, as well as the time flow of the control strategy of the decentralized units. Only following the function test is the control strategy loaded into the decentralized automation system. For changing the parameters of a function block, such must first be opened within a suitable servicing program. Then, the parameters of this function block shown in the servicing program can be changed by the user. If a number of parameters of a control loop must be changed, then the corresponding individual function blocks must be sequentially found, opened, and the required parameter changes effected within the servicing program. A re-parametering during operation of the field device, or the decentralized automation system, is, thus, not possible.
Additionally, it has long been possible to store data and process values in the control loop of a decentralized automation system, either globally in the control system or locally in the field devices. In the case of the local storage, however, this possibility is exclusively the storage of data, parameters and process values that have arisen in the particular field device. Data, parameters and process values of other field devices can not be stored.